An amphibious vehicle capable of traveling on water and land is used as a tour vehicle, a water rescue vehicle, a disaster response vehicle, and the like. Generally, the amphibious vehicle includes a propulsion device such as a propeller or a water jet for travel on water and a drive device such as wheels and tracks for travel on land, for one power source such as an engine or a motor. Furthermore, the amphibious vehicle includes a power distribution device for distributing the power from the power source to the propulsion device for travel on water and the drive device for travel on land.
The amphibious vehicle can travel on land and water by controlling the power distribution device to use one or both of the drive device and the propulsion device depending on a situation. The amphibious vehicle travels on land by activating the drive device. After transition from land to water, the amphibious vehicle stops the drive device and travels on water by activating the propulsion device. In transition from water to land, the amphibious vehicle activates the drive device in addition to the propulsion device activated for travel on water (Patent Document 1).
Such control of the power distribution device can be divided into three modes of a land travel mode, a water travel mode, and a landing mode based on a movement state of the amphibious vehicle. The land travel mode is control performed when the amphibious vehicle is traveling on land, and sets the amphibious vehicle to a state where the propulsion device is stopped and only the drive device is activated. The water travel mode is control performed when the amphibious vehicle is traveling on water, and sets the amphibious vehicle to a state where the drive device is stopped and only the propulsion device is activated. The landing mode is control performed when the amphibious vehicle performs the transition from water to land, and sets the amphibious vehicle to a state where the drive device and the propulsion device are activated.
In the control described above, the drive device is activated in the land travel mode and the landing mode. In the land travel mode, the drive device is used in a wide range up to a point where the engine rotates at high speed, i.e. used in a wide range up to a point where the amphibious vehicle travels at high speed. Meanwhile, in the landing mode, the drive device is used only in a narrow range where the engine rotates at low speed, i.e. used only in a narrow range where the amphibious vehicle travels at low speed.
The drive device of the amphibious vehicle is thus formed of a mechanism suitable for the land travel mode whose usage range is wide. Specifically, the drive device of the amphibious vehicle is set such that the vehicle speed of the amphibious vehicle and the engine torque required to activate the drive device with respect to the engine speed are appropriate in the land travel mode.
Moreover, the propulsion device is activated in the water travel mode and the landing mode. In the water travel mode, the propulsion device is used in a wide range up to a point where the engine rotates at speed, i.e. used in a wide range up to a point where the amphibious vehicle is travels at high speed. Meanwhile, in the landing mode, the propulsion device is used only in a narrow range where the engine rotates at low speed, i.e. used only in a narrow range where the amphibious vehicle travels at low speed.
The propulsion device of the amphibious vehicle is thus formed of a mechanism suitable for the water travel mode whose usage range is wide. Specifically, the propulsion device of the amphibious vehicle is set such that the vehicle speed of the amphibious vehicle and the engine torque required to activate the propulsion device with respect to the engine speed are appropriate in the water travel mode.
Since the drive device is set to be suitable for the land travel mode and the propulsion device is set to be suitable for the water travel mode as described above, the engine speed and the engine torque are in an appropriate state in the land travel mode in which only the drive device is activated and in the water travel mode in which only the propulsion device is activated.